Process for producing a strong-acid cation exchange resin

ABSTRACT

A strong-acid cation exchange resin in acid form is contacted with an alkylcarhamoyl alkylthioester in the presence of water for producing a strong-acid cation exchange resin comprising a plurality of acid groups being partially neutralized with a mercaptoalkylamine. The produced partially neutralized cation exchange resin is useful as a catalyst in a process of producing a bisphienol by reaction of a phenolic compound with a carhonyl compound.

This application is a 371 of PCT/US01/28215 Sep. 6, 2001, which claimsbenefit of provisional application No. 60/233,679, Sep. 19, 2000.

BACKGROUND OF THE INVENTION

The present invention relates to a process for producing a strong-acidcation exchange resin which comprises acid groups being partiallyneutralized with a mercaptoalkylamine.

Strong-acid cation exchange resins which comprise acid groups beingpartially neutralized with a mercaptoalkylamine and their use in theproduction of bisphenols is known in the art.

U.S. Pat. No. 3,394,089 describes a process for the preparation ofbisphenol A from acetone and phenol in the presence of a strong-acidcation exchange resin wherein from 5 to 25 percent of the acid groupsare neutralized with a C₁₋₄-alkyl mercaptoamine. The mercaptoalkylamineis an effective promoter for the acid catalyzed condensation of phenoland acetone. The neutralization is carried out by direct contact withthe C₁₋₄-alkyl mercaptoamine or by exchange with its amine salt.According to the example an aqueous slurry of sulfonic acidcation-exchange resin in acid form is contacted with an aqueous solutionof mercaptoethyl amine hydrochloride.

U.S. Pat. No. 5,212,206 discloses that the partially neutralized cationexchange resin as described in U.S. Pat. No. 3,394,089 is unsuitable inthe bisphenol production because of the instability of the catalyst. Toovercome this deficiency, U.S. Pat. No. 5,212,206 teaches that thestrong acid cation-exchange resin is neutralized with a mercaptoamine inan anhydrous medium.

U.S. Pat. No. 4,584,416 discloses partial neutralization of a sulfonatedion exchange resin by means of an N-alkylamino alkyirnercaptanhydrochloride or hydrotosylate salt.

U.S. Pat. No. 5,589,517 discloses the partial neutralization of asulfonated ion exchange resin by contacting the ion exchange resin withan N,N-dialkylmercaptoalkylamine, an N-mercaptoalkylpyrrolidine or anN-mercaptoalkylpiperidine.

U.S. Pat. No. 3,760,006 teaches that the modification of a strong-acidcation exchange resin in acid form by partial neutralization with athiazolidine yields an improved catalyst for the preparation ofbisphenol.

U.S. Pat. No. 4,595,704 discloses that known methods for producingpartially neutralized ion-exchange resins employ azirine compounds whichare somewhat hazardous. The U.S. patent suggests the use of less costlyand less hazardous N-(2-mercaptoalkyl)amides to prepare a strong-acidcation exchange resin which is partially neutralized with anaminoalkanethiol.

U.S. Pat. No. 4,918,245 teaches that it has been known that markedlydecreased amounts of Dianin's compound are produced as by-products inthe bisphenol A production if an ion exchange resin is used as acatalyst of which the functional groups are modified with mercaptogroups, such as by reaction with a mercaptoethylamine. On the otherhand, the US patent also discloses that o,p′-isomer is still formed as aby-product in a large amount.

Unfortunately, sulfur-containing compounds which comprise a thiol groupare sensitive to attack by oxygen and metals. Accordingly, the storageof these compounds without special care results in a reduced activity ofstrong-acid cation exchange resins which are partially neutralized withsuch compounds. When the partially neutralized strong-acid cationexchange resin is used as a promoter for producing bisphenol A, avariation in promoter quality may result in product variation, which isundesirable.

Accordingly, it would be desirable to find a new process for producing astrong-acid cation exchange resin comprising a plurality of acid groupsbeing partially neutralized with a mercaptoalkylamine. It would beparticularly desirable to find a process wherein the starting materialused for neutralization is not sensitive to attack by oxygen and metals.

SUMMARY OF THE INVENTION

One aspect of the present invention is a process for producing astrong-acid cation exchange resin comprising a plurality of acid groupsbeing partially neutralized with a mercaptoalkylamine, wherein astrong-acid cation exchange resin in acid form is contacted with analkylcarbamoyl alkylthioester in the presence of water.

Another aspect of the present invention is a process of producing abisphenol wherein a phenolic compound is reacted with a carbonylcompound in the presence of the strong-acid cation exchange resinproduced according to the process above.

Yet another aspect of the present invention is a process for isomerizingby-products resulting from the production of a bisphenol by reaction ofa phenolic compound with a carbonyl compound wherein the by-products arecontacted with a strong-acid cation exchange resin produced according tothe process above.

DETAILED DESCRIPTION OF THE INVENTION

The alkylcarbamoyl alkylthioester can be prepared by known methods, suchas taught in Houben-Weyl, Volume IX, page 750, Georg Thieme editorStuttgart, 1955. It is not sensitive to attack by oxygen and metals to asubstantial degree.

Preferred alkylcarbamoyl alkylthioesters are represented by the formulaI

R¹—C(O)—NH—R²—S—C(O)—R³  (I)

wherein

R¹ and R³ each independently is a C₁₋₄-alkyl group, preferably methyl,ethyl or propyl; and

R² is a C₂₋₆-alkylene group.

More preferably, R¹ and/or R³ is methyl. Most preferably, both groups R¹and R³ are methyl.

Useful C₂₋₆-alkylene groups are ethylene, n-propylene, isopropylene,n-butylene, isobutylene, n-pentylene, isopentylene, neopentylene,n-hexylene and all hexylene isomers. The most preferred C₂₋₆-alkylenegroup is n-propylene.

Preferred alkylcarbamoyl alkylthioesters are thioacetylalkyl amides.More preferred are thioacetylalkyl acetamides, such as thioacetylethylacetamide, thioacetyl-n-propyl acetamide, thioacetyl-isopropylacetamide, thioacetyl-n-butyl acetamide, thioacetyl-isobutyl acetamide,thioacetyl-n-pentyl acetamide, thioacetyl-isopentyl acetamide,thioacetyl-neopentyl acetamide, thioacetyl-n-hexyl acetamide or isomersthereof The most preferred alkylcarbamoyl alkylthioester is a compoundof formula I wherein R¹ and R³ each are methyl and R² is n-propylene,that means thioacetyl-n-propyl acetamide.

The process of the present invention is employed to modify a strong-acidcation exchange resin. Strong-acidic cation exchange resin are known inthe Art, see for example “Ullmann's Enzyklopaedie der TechnischenChemie”, 4th Edition, Vol. 13, pages 297 and following. Usually theyhave a polymeric matrix and functional ion exchange groups.

One known type of matrix is based on phenol/formaldehyde or benzenecondensation polymers that are cross-linked with an aldehyde, achlorinated hydrocarbon or an epoxy compound. The preferred matrixes arecross-linked polystyrene or cross-linked poly(alpha-methylstyrene) or across-linked polymer of styrene or alpha-methylstyrene which issubstituted at the benzene ring with C₁₋₆-alkyl, for example methyl,ethyl, tert. butyl or isopropyl, or with halogeno-C₁₋₆-alkyl, such aschloromethyl, or with aminomethyl. The cross-linking agent preferably isdivinylbenzene or trivinylbenzene.

The functional groups can be directly or indirectly bound to thepolymeric matrix. For example the functional groups can be bound to thepolymeric matrix via alkylene groups such as C₁₋₃-alkylene groups,preferably ethylene or methylene with methylene being the most preferredgroup.

Functional groups typically are —SO₃H or -PO₃HR groups wherein R ishydrogen, a C₁₋₆-alkyl group, such as a methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, the pentyl or hexyl groups, aC₃₋₆-cycloalkyl group, such as cyclohexyl, or aryl, such as phenyl orbenzyl. The most preferred functional group is —SO₃H. A part of thefunctional groups can be present in the salt form, for example in thealkali or alkaline earth metal salt form. However, preferably more than95 percent, more preferably more that 99 percent, most preferablysubstantially all functional groups are in the acid form prior topartial neutralization according to the process of the presentinvention.

Examples of suitable strong-acid cation exchange resins includeperfluorinated sulfonic acid resins, strong-acid resins prepared byphosphonation of styrene-divinylbenzene resins, sulfonatedphenol-formaldehyde resins, sulfonated polystyrene resins, sulfonatedstyrene-divinylbenzene resins and polymers such as those disclosed inU.S. Pat. Nos. 4,303,551 and 4,330,654. The sulfonated resins arecommercially available as gelular and macro-reticular types.Particularly suitable are aromatic sulfonic acid resins having a cationexchange capacity of at least 0.5 meq/g dry weight and advantageously2.0 meq/g. Commercial strong-acid cation exchange resins prepared by thesulfonation of a styrene-divinylbenzene resin, as described, forexample, in U.S. Pat. Nos. 2,597,438; 2,642,417 or 3,037,052 are mostpreferably used. Such commercial sulfonic acid resins are Dowex 50resins, Amberlite IR-120 resin, Amberlite 200 resin and Duolite C20resin which normally have an exchange capacity of from 4 to 5.5 meq/gdry weight (Dowex, Amberlite and Duolite are trademarks).

The strong-acid cation exchange resin is partially neutralized bycontacting it with an alkylcarbamoyl alkylthioester in the presence ofwater. Typically about a molar equivalent of alkylcarbamoylalkylthioester is employed per equivalent of hydrogen ions to beneutralized. Water is employed in an amount sufficient to hydrolyze thealkylcarbamoyl alkylthioester to the corresponding mercaptoalkylamine.Without wanting to be bound to a theory, it is believed that thehydrolyzation of the alkylcarbamoyl alkylthioester to the correspondingmercaptoalkylamine and the partial neutralization of the acid groups ofthe cation exchange resin occur simultaneously. The hydrolysis issubstantially quantitative. Typically from 0.2 to 5, preferably from 0.5to 3, volumes of water are employed per volume of resins beads. Watercan be used alone or in combination with an organic solvent. Preferredorganic solvents are ketones, such as acetone, alcohols, such asmethanol or ethanol, phenols, such as phenol, or aromatic hydrocarbons,such as toluene. The partial neutralization of the catalyst with thealkylcarbamoyl alkylthioester is preferably carried out at a temperatureof from 50 to 120° C., more preferably from 80 to 110 ° C., mostpreferably at reflux temperature. The extent of neutralization of thecatalyst may vary widely. Typically from 5 to 60 mole percent,preferably from 10 to 40 mole percent, more preferably from 15 to 35mole percent of the acidic groups of the cation exchange resin areneutralized. The degree of neutralization is readily verified bymeasuring via conventional methods, such as titration using NaOH, theion exchange capacity of the resin before and after neutralization.

The produced partially neutralized strong-acid cation exchange resin isan effective catalyst for the preparation of many bisphenols by reactionof a phenolic compound with a carbonyl compound.

The reaction of a phenolic compound with a stoichiometric excess of acarbonyl compound is known in the art. The process is described ingeneral in U.S. Pat. Nos. 3,049,569 and 4,107,218 and in the referencescited therein. The molar ratio between the phenolic compound and thecarbonyl compound preferably is between 2:1 and 45:1, more preferablyfrom 4:1 to 14:1.

Useful phenolic compounds should be unsubstituted in para position, butthey can be substituted in ortho- or meta-position with one or morenon-reactive groups, such as alkyl or halo. Preferred phenolic compoundsare those of formula (II)

wherein R⁴, R⁵, R⁶ and R⁷ independently of one another representhydrogen, halogen, preferably chlorine or bromine, or C₁₋₈-alkyl,preferably methyl, ethyl or tertiary butyl.

Preferred examples of the compounds of formula (II) are phenol, mono-,di-, tri- or tetraalkylphenols, such as o-cresol or m-cresol;o-sec.butylphenol, o-tert.butylphenol, 2,6-dimethylphenol,3,5-dimethylphenol, 2-methyl-6-tert.butylphenol,2-isopropyl-5-methyl-phenol, 5-isopropyl-2-methyl-phenol,2-methyl-6-ethylphenol, 2,3,6-trimethylphenol,2,3,5,6-tetramethylphenol, 2,6-ditertiary-butylphenol, 3,5-diethylphenolor 2-methyl-3,5-diethylphenol; chlorophenols, such as o-chlorophenol orm- chlorophenol; dichlorophenols or bromophenols, such as o-bromophenol.

The carbonyl compound employed for producing the bisphenol can be aketone or an aldehyde. Preferred carbonyl compounds are those of thefollowing formula III

wherein

R⁸ is an aliphatic, cycloaliphatic, aromatic or heterocyclic group, and

R⁹ is hydrogen or an aliphatic, cycloaliphatic, aromatic or heterocyclicgroup or

R⁸ and R⁹ together represent a divalent aliphatic or aromatic group.

Preferred groups R⁸ and R⁹ are C₁₋₈-alkyl, C₅₋₆-cycloalkyl, C₅₋₁₀-aryl,preferably phenyl, or C₇₋₁₂-aralkyl, preferably phenyl-C₁₋₄-alkyl, morepreferably benzyl. These groups are optionally halogenated. When R⁸ andR⁹ together represent a divalent aliphatic group, the group preferablyis —(R¹⁰ CR¹¹)_(n)— wherein R¹⁰ and R¹¹ in each occurrence individuallyselectable are hydrogen or C₁₋₆-alkyl, such as methyl or ethyl, and n isan integer from 4 to 7, preferably 4or 5.

Examples of suitable ketones include, for example, acetone,1,3-dichloroacetone, methyl ethyl ketone, diethyl ketone, dibutylketone, methyl isobutyl ketone, cyclohexanone, fluorenone, preferably9-fluorenone, propionylphenone, methyl amyl ketone, mesityl oxide,cyclopentanone or acetophenone. Examples of suitable aldehydes includeformaldehyde, acetaldehyde, propionaldehyde, butyraldehyde andbenzaldehyde. The most preferred carbonyl compound is acetone.

The phenolic compound and the carbonyl compound are preferably reactedat a temperature of from 35 to 100° C., more preferably from 40 to 90°C., most preferably from 45 to 85 ° C.

The strong-acid cation exchange resin modified according to the presentinvention is particularly useful in the production of bisphenol A fromphenol and acetone. It has been surprisingly found that a higher purityof the 4,4′-dihydroxy-2,2-diphenylpropane (commonly called thep,p′-isomer of bisphenol A or simply bisphenol A) can be achieved whenusing the strong-acid cation exchange resin modified according to thepresent invention as a catalyst instead of a strong-acid cation exchangeresin which has been modified with dimethylthiazolidine or cysteaminehydrochloride, both of which are commonly used modifiers. When using thestrong-acid cation exchange resin modified according to the presentinvention, the amount of the undesired by-product2,4′-dihydroxy-2,2-diphenylpropane (commonly called the o,p′-isomer ofbisphenol A) is generally only up to about 2 percent, based on theweight of the p,p′-isomer of bisphenol A. This amount is generally atleast about 15 percent lower, in many cases even at least about 20percent lower than the amount of the o,p′-isomer of bisphenol A that isobtained in the presence of a corresponding strong-acid cation exchangeresin which has been modified with dimethylthiazolidine or cysteaminehydrochloride.

Furthermore, the strong-acid cation exchange resin produced according tothe present invention is useful as a catalyst for isomerizingby-products resulting from the above-described production of abisphenol, preferably for isomerizing by-products which result from theproduction of bisphenol A and which include2,4′-dihydroxy-2,2-diphenylpropane. The produced strong-acid cationexchange resin is particularly useful for isomerizing2,4′-dihydroxy-2,2-diphenylpropane to4,4′-dihydroxy-2,2-diphenylpropane. The isomerization process isgenerally known in the art.

The following examples are provided to illustrate the present invention.The examples are not intended to limit the scope of the presentinvention and they should not be so interpreted. Amounts are in weightparts or weight percentages unless otherwise indicated.

EXAMPLE 1 Preparation of Thioacetylpropyl Acetamide

58 g of thioacetic acid are placed in a flask. 350 g of a 15 percentsolution of sodium ethoxide in ethanol is added drop by drop undercooling by nitrogen and ice. Afterwards 320 g of a 12.4 percent solutionof 3-chloropropylamine hydrochloride in ethanol are added to the abovesolution. The mixture is heated under reflux for 1 hour, cooled to roomtemperature and filtrated. The ethanol is evaporated and the residue isdissolved in acetone to precipitate any residual sodium chloride. Afterfiltration the acetone is removed. Thioacetylpropyl acetamide remains asviscous oil.

Preparation of the Partially Neutralized Cation Exchange Resin

30 g of thioacetylpropyl acetamide produced above, 500 ml of a wet,strong-acid cation exchange resin which comprises sulfonic acid groupsand a polymer matrix of styrene cross-linked with 4 percent ofdivinylbenzene, 1000 ml of water and 50 ml of methanol are placed in aflask. The strong-acid cation exchange resin is commercially availableunder the trademark DOWEX 50WX4 from The Dow Chemical Company and has acation exchange capacity of 1.2 meg/ml (5.3 meq/g). The mixture isstirred under reflux for 6 hours and then cooled to room temperature.The resin is filtrated and washed with acetone and water. Analysis ofthe resin by titration with NaOH shows that 23 percent of its acidcapacity is neutralized with 3-mercaptopropylamine.

Comparative Example A

4 g of 2,2-dimethylthiazolidine, 100 ml of the above-describedstrong-acid cation exchange resin, which is commercially available underthe trademark DOWEX 50WX4 from The Dow Chemical Company, and 250 ml ofwater are stirred for one hour at room temperature, then filtrated andwashed with another 250 ml of water.

A cation exchange resin is prepared of which 25 percent of its acidcapacity is neutralized with 2,2-dimethylthiazolidine.

Comparative Example B

4 g of 2-mercaptoethylamine hydrochloride (also designated as cysteaminehydrochloride), 100 ml of the above-described strong-acid cationexchange resin, which is commercially available under the trademarkDOWEX 50WX4 from The Dow Chemical Company, and 250 ml of water arestirred for one hour at room temperature, then filtrated and washed withanother 250 ml of water.

A cation exchange resin is prepared of which 25 percent of its acidcapacity is neutralized with 2-mercaptoethylamine.

Use of the Modified Catalyst

A stainless steel reactor column is charged with 500 ml of the partiallyneutralized cation exchange resin prepared according to Example 1 orComparative Example A or B. The resin is dried by flushing the resin bedwith twice its volume of phenol at 60° C. The catalyst is ready for use.The catalyst activity is tested by pumping a liquid consisting of phenoland acetone in a molar ratio of 10:1 at a speed of 4ml/min. through thecolumn containing the catalyst at 70° C. The amounts of bisphenol A (thep,p′-isomer) and of the o,p′-isomer of bisphenol A in the resultingproduct mixture are analyzed by gas chromatography. The percento,p′-isomer, based on the weight of the p,p′-isomer of bisphenol A, islisted in Table 1 below.

TABLE 1 (Comparative) Compound used for Percent Percent o, Exampleneutralization Neutralization p'-isomer 1 Thioacetylpropyl acetamide 231.9 A Dimethylthiazolidine 25 2.5 B 2-mercaptoethylamine 25 2.5hydrochloride

percentage of o,p′-isomer, that means a purer product is obtainedaccording to Example 1, as compared to Comparative Examples A and B. Thesmall difference in neutralization of the acid groups (23 percent inExample 1 but 25 percent in Comparative Examples A and B) does notinfluence the percentage of o,p′-isomer.

What is claimed is:
 1. A process for producing a strong-acid cationexchange resin comprising a plurality of acid groups being partiallyneutralized with a mercaptoalkylanine, wherein a strong-acid cationexchange resin in acid form is contacted with an alkylcarbamoylalkylthioester of the formula I R¹—C(O)—NH—R²—S—C(O)—R³  (I) wherein R¹and R³ are each independently a C₁₋₄-alkyl group, and R² is aC₂₋₆-alkylene group in the presence of water.
 2. The process of claim 1wherein R¹ or R³ or both are methyl.
 3. The process of claim 2 whereinin formula I R¹ and R³ each are methyl and R² is propylene.
 4. Theprocess according to claim 1 wherein the strong-acid cation exchangeresin comprises sulfonic acid groups and has an initial cation exchangecapacity of at least 0.5 meq/g dry resin in acid form.
 5. The processaccording to claim 1 wherein the strong-acid cation exchange resin is asalfonated styrene-divinylbenzene resin.
 6. The process according toclaim 1 wherein from 5 to 60 mole percent of the acidic groups areneutralized.
 7. A process for producing a bisphenol wherein a phenoliccompound is reacted with a carbonyl compound in the presence of astrong-acid cation exchange resin produced according to the process ofclaim
 1. 8. The process of claim 7 wherein phenol is reacted withacetone.